d <-
tibble::tibble(a = rnorm(20),
b = rnorm(20),
c = rnorm(20))
output <- vector("double", ncol(d)) # 1. output
for (i in seq_along(d)) { # 2. sequence
output[[i]] <- median(d[[i]]) # 3. body
}
output[1] 0.4385698 -0.5059396 0.0746266